1. Field of the Invention
The invention relates to a method for the manufacture of oxidic sintered nuclear fuel bodies by a heat treatment of blanks obtained from UO.sub.2 starting powder or a mixture of UO.sub.2 and PuO.sub.2 starting powder at a temperature in the range of 1000.degree. C. to 1400.degree. C. in a gas atmosphere which initially has oxidizing action and subsequently reducing action.
2. Description of the Prior Art
Such a method is known from German Published Non-Prosecuted Application No. 28 55 166. In this method, the blanks are obtained by compacting nuclear fuel powder which, for adjusting the micro-structure, is reacted and mixed with grain size growth promoting sintering additives such as U.sub.3 O.sub.8. Technically pure CO.sub.2 is, for instance, used as the oxidizing gas atmosphere. The known method leads to oxidic sintered nuclear fuel bodies with a uniformly fine grain nuclear fuel oxide matrix in the micro-structure in which coarse islands are embedded only at the points which had originally been occupied by the grain growth promoting sintering additives. During the nuclear fission processes in the oxidic sintered nuclear fuel bodies in a nuclear reactor which is in operation, the sintered nuclear fuel bodies obtained in accordance with the known method liberate less gaseous or highly volatile nuclear fission products and are subjected to less post densification than sintered nuclear fuel bodies with an absolutely uniform micro-structure of very small grain size. Fuel rods which are filled with the sintered nuclear fuel bodies obtained by the known method therefore develop a smaller internal pressure in the cladding tube than fuel rods which are filled with oxidic sintered nuclear fuel bodies which have an absolutely uniform micro-structure of this small grain size.